Tandem white organic light emitting diodes (WOLEDs) are fabricated with blue and red unit devices connected by a transparent Al:LiF/molybdenum oxides (MoO₃) connecting layer. The blue and red unit devices have been fabricated with standard structure based on 8 % iridium (III)bis(4,6-(di-fluorophenyl)-pyridinato-N,C2') picolinate (FIrpic) doped in N,N'-dicarbazolyl-3,5-benzene (mCP) and 8 % bis (1-phenylisoquinolinato-N,C² )iridium(acetylacetonate) ((piq)2Ir(acac)) doped in 4,4'-N,N'-dicarbazolebiphenyl (CBP), respectively. The doping concentration of LiF in the Al:LiF composite layer is 10 % and the Al:LiF layer thickness is varied from 3 nm up to 10 nm to optimize the performance of tandem WOLEDs while the MoO3 thickness is fixed at 10 nm. We found that electron injection efficiency decreases for thicker Al:LiF layer, resulting lower electroluminescence (EL) efficiency. The maximum brightness and current luminous efficiency for the tandem WOLEDs are about 32,230 cd/m² and 18.5 cd/A, respectively, for the Al:LiF (10 %) thickness of 3 nm.

Date Published: 2 September 2009
PDF: 7 pages
Proc. SPIE 7415, Organic Light Emitting Materials and Devices XIII, 74151X (2 September 2009); doi: 10.1117/12.826791

Published in SPIE Proceedings Vol. 7415:
Organic Light Emitting Materials and Devices XIII
Franky So; Chihaya Adachi, Editor(s)